York 00497VIP manual Microboard, Refer To Fig, Service

Service

MICROBOARD

(REFER TO FIG. 31 - 36)

The Microboard contains the operating software (Program), microprocessor (Micro), and supporting circuits for the Micro.

The Program is a set of instructions to control remote chillers and the display. It also contains the Display messages and screens. It is stored in a memory device called a flash memory card. This is a type of nonvolatile memory that can be read from or written to, but requires the locations to be erased before they are written to. With the exception of a write/read sequence that occurs during the Boot-up process explained below, this device is used primarily as read-only in this application. A write protect switch is located on the left edge of the card as shown in Fig. 32. It must be placed in the “Write Enabled” position in order to allow successful Boot-up. The card is located in socket location U46 (Ref. Fig. 31). It connects to the Board via an Elastomeric connector that is a silicon rubber strip embedded with silver conductors. The Card can be removed from its socket by using the thumb to press down on the socket’s plastic tension spring. The card is installed by inserting it into the socket/holder and pressing on the surface of the Card until it snaps into place. The Memory card is a replaceable component. Refer to the YORK Renewal Parts List. The version of the Memory card is an alphanumeric code that represents the application and revision level. The version is printed on a label adhered to the memory card’s surface. The version code is as follows:

C. RCC. 01. XX.

Revision level. Increments 00, 01 etc.

Product Code for OptiView RCC

Remote Control Center

Commercial

The Micro monitors and controls the chiller by reading and executing the Program instructions in a sequence determined by the Program. Under Program control, the Micro communicates with the chillers via RS-485 serial communications to determine the operating conditions. As operating conditions require, status messages are retrieved and displayed. The Keypad is read as Digital Inputs. When an operator presses a key to request a display, the Micro interprets the request, retrieves the display from the Program and displays it. The Program assembles data in the correct format for transmission

through the Serial Data Ports to the chiller(s) and peripheral devices. The Program also instructs the Micro to respond to requests from peripheral devices for serial data transmissions.

The Mux (multiplexer) is a switching device that only allows one analog input through at a time. The inputs are selected sequentially by the Micro per Program instructions.

The A/D Converter converts each analog input to a 12-bit word. In this form, the values can be stored in memory devices, compared to values in the Program, transmitted through Serial Ports or sent to the Display Controller for display. Control signals to start conversion process are from the Micro via the FPGA.

The Watchdog circuit monitors the +5VDC supply from the Power Supply to determine when a power failure is occurring. Just prior to the supply decreasing to a level where the Micro and supporting circuits can no longer operate, it applies a reset signal to the Micro. The Micro responds by shutting down the remote control center and retrieving the Power Failure message from the Program and sending it to the Display Controller for display. Similarly, when power is first applied after a power failure, it maintains the Micro in a reset state until the +5VDC has returned to a sufficient level. The Watchdog circuit also assures that all the Program instructions are being performed and that the Program has not latched-up, bypassing important safety thresholds. If the Program has latched-up, the Micro displays WATCHDOG – SOFTWARE REBOOT message.

The Program Jumpers (Table 2) and Program Switches (Table 3) are used to alter the Program operation or configure the Microboard hardware for specific operation. This allows the Program and Microboard to be universal for all applications. Refer to Table 2 and 3 for the function of each jumper and switch. The position of some can be determined and set by the Service Technician to meet the desired operation. The position of others is dictated by the size, type or style of certain Control Center components and thus the position is determined by the YORK Factory. The required position of each is listed in these tables. The Program Jumpers are wire bridges that are either left in place or cut. The Program Switches are miniature switches that are placed in either the ON or OFF position.

68 YORK INTERNATIONAL